已知x+y=7，xy=5，则（x-y）2的值为 [ ]
A．39
B．29
C．25
D．27
答案：B
—It's a fine day today. Why not go out for a walk?
—_____. [ ]
A. Good luck
B. That's OK
C. It's very kind of you
D. Good idea
膀胱炎与肾盂肾炎都有的症状是（）
A.血尿
B.尿频、尿急、尿痛
C.蛋白尿
D.尿菌落计数>1000／ml
E.少尿
